Karlsruhe, Germany - Germany's top court approved Wednesday some of the world' most rigorous restrictions on genetically modified crops, ruling they were in accordance with the country's constitution.

One of Germany's 16 states, Saxony-Anhalt, had challenged a federal law that obliges a farmer to pay damages if bees and wild insects carry pollen from a GM crop to a neighbour's non-GM crop.

Many Germans are deeply suspicious of GM crops, where the DNA of plants is modified in the laboratory to help plants to resist pests. Some opponents have denounced the produce as 'Frankenstein food.'

The federal constitutional court in Karlsruhe rejected complaints that a public register of the fields where GM crops grow was a breach of privacy. Farmers say the register helps militant anti-GM campaigners to destroy crops by trampling or contaminating them.

But the court approved legislation which Chancellor Angela Merkel has insisted is a fair compromise between the anti-GM activists and the big mechanized farms that are eager to improve crop yields with new-style pest-resistant strains.

'Given that the state of knowledge about the long-term consequences of deploying genetic modification is not fully researched, the legislative arm has an especial duty of care,' the court judgement said.

Farmers must publicly disclose what seed they used. The court also approved a no-fault-liability rule which obliges a farmer to compensate his neighbours for any loss in market value of their crops if the natural and GM variants become mixed.

GM farmers will have to pay the damages even if there was no obvious fault with their agricultural technique.

Saxony-Anhalt state is part of eastern Germany, where commercial farming with very large fields and advanced technology dominates. In the rest of Germany, farming is mainly on family-run smallholdings, which tend to show less interest in GM seed.